Description
This device consists of a differential with helical gears: it has the ability to lock progressively up to 35% when pulling and 25% when releasing. Efforts were made to limit the percentage of release so as not to affect the functionality of the ABS during braking.
How does the self-locking differential work? First, let's consider how the standard front differential on our Panda works.
The differential is a device that splits the torque coming from the gearbox exactly in half to each of the two half-shafts, regardless of the difference in the rotational speeds of the two wheels on the axle itself. Therefore, as you can see in the figure, if the torque input to the differential is 100 (the units are completely arbitrary), 50 torque will end up on each wheel.
There's another important parameter to consider, however: tire grip. Torque can be "discharged" to the ground up to the wheel's grip limit ; this limit is therefore proportional to the load fraction acting on the wheel and the grip coefficient, which depends primarily on the consistency of the ground.
Therefore, if one of the two front wheels ends up in an area with less grip (for example, in mud), the torque that can be transmitted to the ground by that wheel is reduced, as the wheel itself reaches a slipping condition. Due to the property of the differential mentioned above, which is that it is a mechanism that equally divides the input torque, the same torque value will also be applied to the other wheel, which still maintains good grip.
As can be seen from the previous figure, if the value of the slip limit torque of the front left wheel is 20, the right wheel will also be able to unload a torque of 20 to the ground. And therefore the total traction of the front axle is reduced to a value of 40, significantly lower than the 100 of the previous example.
If we install the Prometeo self-locking differential in place of the standard differential, traction improves in these cases. Let's see how and by how much.
First of all, in conditions of good and uniform grip, the self-locking differential behaves like a normal differential, as can be seen in the following figure.
However, if one wheel loses traction, the self-locking differential transfers more torque to the other wheel. The total torque delivered to the ground by the front axle is therefore greater than that delivered by a common differential. The following figure clearly illustrates this operating mode.
The 35% lockup percentage is the best compromise found through numerous tests conducted on various surfaces. It's important to remember that an excessive lockup percentage would have made the vehicle excessively understeer in normal driving, resulting in handling problems. Conversely, too little lockup would have reduced the benefits of the self-locking brake, making it objectively useless.
With the Prometeo self-locking differential for the front of the Panda 4x4 we obtain the following important results:
-in normal driving on asphalt and surfaces with good grip, no differences in driving feel are felt compared to the standard differential;
-if the surface becomes slippery (ice, snow, rain) or the vehicle is used on loose or unstable terrain (mud, sand) the Prometeo differential significantly increases front traction.
With the Prometeo self-locking differential you can perform a 180° turn on asphalt at any speed you want, without feeling the wheels slip... Try it and believe it!!
Fiat Panda 4x4 mod. 169
The kit for sale consists of the differential and the 2 SKF tapered roller bearings that support it
The PROMETEO front self-locking differential
The differential with crown and transmission mounted
The assembly phase on the crankcase
The box with the satellite slots
Differential helical gears